Piezoelectric device



Sept. 14, 1943. H, M EACH 2,329,321

PIEZOELECTRIC DEVICE Filed Sept. 17, 1942 'o' Sheets-Sheet 1 5 .4. j T TZV EKTQR 91% ATT RNE H. M. BACH PIEZOELECTRIC DEVICE Sept. 14, 1943.

Filed Sept. 17, 1942 5 Sheets-Sheet 3 INVENTOR BY ATTORNEY Patented Sept. 14, 1943 2,329,321 PIEZOELECTRIC DEVICE Henry M. Bach. Lawrence. N. Y.. assignor to Premier Crystal Laboratories, Inc., New York, p N. Y., a corporation of New York Application September 17, 1942, Serial No. 458,634

8 Claim.

This invention relates to piezo-electric devices and more particularly to improved holders and contacting arrangements for such devices.

A principal object is to provide a small, compact holder for piezo crystals wherein the frequency adjustment is maintained even though the unit is subjected to strong shocks or vibrations such as are encountered when the unit is used aboard a mobile vehicle or the like.

Another object is to provide an improved moisture-proof and airtight crystal holder, wherein the assembly of theparts within the holder can be effected rapidly and without employing any soldered or similar permanent connections to and from the crystal electrodes or other movable'parts,

A further object is to provide an improved form of plug-in crystal holder.

A feature of the invention relates to an improved contaet making arrangement for plug-in type crystal holders.

Another feature relates to the novel organization, arrangement and relative location and interconnection of parts whereby a stable, sensitive,. durable and moisture-proof piezo crystal unit is obtained.

Other features and advantages not specifically set forth will be apparent after a consideration of the following detailed descriptions and the appended claims.

In the drawings which represent one preferred form of the invention,

Fig. 1 is a front face view of the device according to the invention.

Fig. 2 is a rear view of Fig. 1.

Fig. 3 is a view like Fig. 1 but with the front cover plate and sealing gasket removed.

Fig. 4 is a view of Fig. 1 with the cover plate removed to show the sealing gasket, but with certain parts omitted. Fig. 5 is a sectional the line 5-5 thereof.

Fig. 6 is a sectional view of Fig. 3 taken along the device shown in the line 6-6 thereof.

view of Fig. 1 taken along vibrations or jars. Furthermore, the requirements of compactness and light weight restrict the usefulness of the conventional type of crys- -tal holder and especially where such holder must has two through openings 3, 4 to receive the threaded shanks 5, 6 of a pair of plug-in prongs 1, 8. These prongs are of any wellknown construction having, for example, a bowed metal contact arm or terminal joined to the threaded shanks. Each prong has a polygonal shoulder 9 for tightening purposes, and washers l0, H the latter being or rubber, "neoprene or other similar material.

The cavity l2 of the housing is of any desired shape, e. g., square or rectangular and communicates with two smaller rectangular cavities i3, ll at its corners which smaller cavities receive the respective metal blocks i5, i6. Blocks i5, it have threaded openings l1, l8 to receive the threaded shanks 5, 8, so-that by turning the prong clockwise it becomes tightened against the front of the housing, and in being tightened it presses and expands the sealing washers Iii, I l to seal the openings 3, 4 against moisture, dust, etc. The upper face of block l5 has a circular recess I9 in which is seated the coiled contact spring 20.

The crystal 2| which is of approximately the same shape and dimensions as those of the inside of cavity 12, is preferably provided on opposite faces with integral metallic coatings 22, and is located between two rigid metal plates 23, 24 having integral raised comers 25, 28. These corners can be formed by offsetting the body of the plate at each corner a predetermined extent, it being understood that the plates are of substantially the same size and shape as the crystal, Thus when the plates are respectively held against the opposite faces of the crystal, the latter is clamped and supported at only its corners, leaving aslight air gap between each plate and the corresponding adjacent crystal face. l

For the purpose of holding the plates 23, 24 firmly but resiliently against the crystal, there is provided a lower bowed metal spring plate 21 having at its forward edge and adjacent one side, a right angled lug with a fiat horizontal arm 28, and a perforated vertical arm 29. Arm 23 is adapted to seat flat against the bottom of cavity 4 and its upper face is in contact with block it. The threaded shank 6 passes through opening 30 and thence into opening l8 in block l6, so that by turning prong 8 clockwise the arm 29 is tightly clamped against the inside wall of cavity I4.

The bowed plate 21 is approximately the same peripheral size and contour as cavity l2 and it is bowed upwardly to support and resiliently contact with plate 23. The upper plate 24 is resiliently pressed against the crystal by a spiral spring 3|, the large end of which engages plate 24, and in order to produce a uniform pressure preferably the bottom coil 32 is bent to lie substantially in a single plane. The small end 33 passes through a central opening 34 in the sealing gasket 35 of neoprene? soft rubber or other suitable moisture-proof and dust-proof airtight sealing material. The member 34 is clamped against the upper face of holder I by a flat metal cover plate 36 which has holes 31 to receive the internally threaded bolts 38 which have shouldered fiat heads 39 to engage the face of plate 36. Holder I has a corresponding set of through holes 40 to receive members 38 and also to receive the fastening screws 4|.' Preferably the face of. holder is recessed around the holes 40 to allow the heads of screws 4| to lie beneath the surface, as shown in Fig. 5.

I have found under certain adverse conditions, reliance cannot be placed entirely on the fiat sealing engagement between member 35 and members and 35 when screws 4| are tightened. In accordance with the invention therefore, the upper face of holder is molded or otherwise provided with an integral raised rib 42 which is continuous. As shown more clearly in Figs. 3 and 8, the rib follows a path which completely surrounds not only the main cavity |2 but also the cavities l3, l4. However it is located so that it excludes the screw holes 40. Consequently when the screws 4| are tightened to compress member 35, a continuous barrier is provided around the crystal cavity since the rib 42 bites into the member 35 thus insuring a completely dustproof, airtight and moistureproof seal for the crystal assembly.

While one particular embodiment has been disclosed, it will be understood that various changes and modifications can be made therein without departing from the spirit and scope of the invention.

What I claim is:

l. A piezo-crystal assembly comprising a boxlike housing of insulation material, a piezo-crystal and cooperating electrodes within the cavity of said housing, a cover plate for said housing, a moisture-proof gasket between said cover-plate and said housing, and a. continuous rib surrounding the housing cavity and cooperating with said gasket to maintain said cavity moisture-proof.

2. A piezo-crystal assembly according to claim 1, in which said rib is integrally molded on the surface of said housing which contacts with said gasket.

3. A piezo-crystal assembly comprising a boxlike housing of insulation material, a main crystal receiving cavity in said housing, a pair of auxiliary cavities in said housing to receive metal contact members, a cover plate for said housing, a flexible gasket for covering said cavities, a continuous rib on the top wall. surface of said housing surrounding said cavities and cooperating with said gasket to maintain said cavities moisture-proof.

4. A piezo-crystal assembly according to claim 3 in which said housing has a plurality of through openings to receive fastening screws to fasten said crver plate and gasket to said housing, and said rib is located so that it excludes said openings. v

5. A piezo-crystal assembly comprising a boxlike housing of insulation material, having a main crystal receiving cavity and a pair of auxiliary cavities, a crystal unit in said main cavity comprising a piezo-crystal, a pair of clamping plates between which said crystal is positioned, spring pressed contact members resiliently engaging said plates, a pair of metal blocks one in each of said auxiliary cavities, means connecting each of said blocks to one ofsaid spring pressed contacts, and a pair of plug-in prongs passing through the wall of said housing and threaded into said blocks. g

6. A piezo-crystal assembly according to claim 5 in which said auxiliary cavities are rectangular in shape and said blocks are rectangular in crosssection. a

'7. A piezo-crystal assembly according to claim 5 in which one of said contact members comprises a bowed spring metal plate having a lug which rests in one of said auxiliary cavities and which is clamped in place by engagement with one of said metal blocks.

8. A piezo-crystal assembly according to claim 5 in which a metal cover plate and intervening moisture-proof gasket are provided for said cavities, and in which one of said contact members is in the form of a spiral spring with the large end in contact with one of said plates and with the smaller end passing through an opening in said gasket to engage said metal cover plate, and a coiled spring is provided having one end in engagement with said cover plate and the other end in contact with the other one of said blocks.

HENRY M. BACH. 

